Herpetologists have described the unusual hunting behavior of snakes from the genus Oligodon. These reptiles kill frogs and toads, and then, having made a hole in the victim's belly with their teeth, eat out its internal organs. For the first time such a feeding method was noted last autumn in O. fascolatus, and now its close relatives O. formosanus and O. ocellatus have been added to the list. Their sightings are described in two articles for the magazine Herpetozoa. Perhaps snakes had to learn how to gut amphibians in order to avoid their poisonous or simply unpleasant-tasting mucus, with which they protect themselves from predators.
Most snakes swallow their victims whole. However, some of them have learned to butcher their prey. For example, snakes from the genera Fordonia and Gerarda tear off and swallow the legs of crabs, and species that feed on snails pull their bodies out of their shells. Last year, a team of researchers led by Danish herpetologist Henrik Bringsøe described an even more unusual example of the feeding behavior of snakes. It turned out that oligodons Oligodon fascolatus, non-poisonous representatives of the Colubridae family living in Southeast Asia, can gut black cicatricial toads (Duttaphrynus melanostictus).
Experts have observed three times how with the help of enlarged posterior teeth on the upper jaw, oligodons make a hole in the toad belly and put the head inside, after which they pull out the internal organs and swallow them. According to experts, this behavior allows snakes to eat amphibians without fear of poison, which is contained in the skin glands behind their ears and on their back. However, the oligodon swallowed the smaller individual of the black cicatricial toad whole in front of scientists.
Since the genus of oligodons includes more than eighty species, Bringso and his colleagues suggested that the habit of gutting amphibians may be characteristic not only of O. fascolatus, but also of its relatives. Four new observations shared with scientists by amateur naturalists from Thailand, Hong Kong and Vietnam have confirmed this hypothesis.
For a fierce hunt for amphibians, representatives of three species were found: O. fasciolatus, for which such behavior has already been described, O. formosanus and O. ocellatus. Decorated bull frogs (Kaloula pulchra) from the Microhylidae family were victims of snakes in three cases, and black cicatrix toad in one.
In the first case, O. fasciolatus pierced its abdomen with his teeth while hunting a frog, but eventually swallowed it whole. In the second, O. formosanus made an incision in the victim's belly and plunged his head inside for twenty minutes. Considering that the snake was rotating around its axis, it is possible that it tore off pieces of internal organs. At the same time, she made no attempts to swallow the frog. In the third case, O. formosanus ate internal organs that had fallen out of the hole in the frog's belly. It is unclear whether the snake killed the amphibian itself or found it already dead. Finally, O. ocellatus was caught when the snake plunged its head into the body of a black scar toad up to the eyes and probably ate the victim's internal organs. However, she then pulled her head out and swallowed the prey whole.
Oligodon ocellatus probably eats the internal organs of the black cicatricial toad (Duttaphrynus melanostictus).
Decorated bull frogs, unlike toads, are not poisonous, but in case of danger they swell and become covered with very sticky and unpleasant-tasting mucus. Possibly, the unusual hunting behavior of oligodons allows them to bypass the defense mechanisms of K. pulchra. Likewise, gutting toads helps to avoid poison from their skin. However, O. ocellatus eventually swallowed the poisonous amphibian whole, which, according to the researchers, indicates the resistance of this species to its toxins.
Bringso suggests that the main function of the back teeth of oligodons is to open the eggs of reptiles, and when hunting frogs and toads, they are used only occasionally.He also notes that all three studied species belong to the O. cyclurus clade - and, possibly, other representatives of it also gut amphibians.
Earlier, we talked about how scientists discovered brown boygs (Boiga irregularis), previously unknown for snakes, on the island of Guam. These reptiles have learned to climb vertical metal posts. To do this, they form an analogue of a lasso from their body, tightly covering the support and braiding the middle of the body with their tail, and then slowly climb up.